The clinical research and manufacturing processes of all vaccines are subject to the oversight of medicines regulatory authorities. Manufacturers are obliged to adhere to set standards in the evidence they provide, which is rigorously evaluated by the medicines regulators. Vaccines are assessed for safety, efficacy and quality before they can be authorised for use. Post-authorisation and surveillance are necessary to ensure that vaccines continue to be suitable for use in the population. 

The efficacy of a Covid-19 vaccine measures its protection against the disease as observed in clinical trials. In order for a vaccine to be considered efficacious, it must demonstrate there is a significant reduction in Covid-19 infections in a group of people who received the vaccine, compared to another group that was not vaccinated. A vaccine with an efficacy of 70% indicates that a vaccinated person is around two-thirds less likely to develop the disease, compared to someone who did not receive it. 

A sufficient number of participants (usually 15 000 or more) must be included in the clinical trial to accurately measure the efficacy of a vaccine. It is important to note that the different clinical trials for vaccines are set up differently and have measured different variables and outcomes. 

One should, therefore, be cautious when comparing the efficacy of different vaccines, unless a head-to-head trial, with the same protocol, delivered and tracked the same way has been conducted.

As Covid-19 infection was deemed a severe disease, a 50% threshold was set such that if a vaccine has this efficacy, it is worth using. Available data has so far shown that the vaccines are better at protecting against severe disease, hospitalisation and death, than against symptomatic disease. 

For vaccines that require two doses, the 1st dose should provide some protection from three or four weeks after vaccination. However, one needs a 2nd dose for stronger and longer-lasting protection. As most people have not yet been vaccinated in many countries, there is still a chance of getting or spreading the infection after being vaccinated. Therefore, it is important to continue observing all Covid-19 protocols such as wearing a mask, hand hygiene and social distancing.

There is ongoing research to determine the effectiveness of the vaccines against emerging variants of the coronavirus. Current data suggests that most vaccines generate sufficient immunity to retain substantial efficacy against most variants, especially for severe diseases, hospitalisation and death.

 If a vaccine becomes less efficacious against one or more variants, it may require a change to its composition to provide protection. This may take time and additional data to fully evaluate.

As more information is being generated, there is a need to do all that is necessary to stop the spread of the virus, to prevent mutations and emergence of variants that may reduce the effectiveness of the available vaccines.

Once a vaccine has been granted emergency use authorisation, continual monitoring of safety is required to ensure that the benefits still outweigh the risks. This is necessary to detect very rare events or any other that could not be detected during clinical trials. 

The regulatory authorities depend on the manufacturers, healthcare workers and the general public to report any suspected adverse events.

Manufacturers of vaccines are required to submit safety reports of their vaccines periodically and also provide a risk management plan that describes how they will monitor and minimise risks associated with vaccine use.

In Namibia, the safety surveillance of all vaccines is integrated with the vaccine delivery system, under the expanded program for immunisation (EPI) of the Ministry of Health and Social Services. Reports from healthcare workers are collected from the health facilities countrywide. 

Healthcare workers, therefore, have a responsibility to diligently report adverse events they suspect in their patients and encourage vaccinated individuals to report any side effects they may experience. This will ensure that these are not only captured but also appropriately managed.

In order to address the reports of serious events that may occur after a person has taken a vaccine, the Ministry of Health and Social Services has appointed a multidisciplinary team of experts who meet periodically to assess if there is a causal link between a vaccine and a reported event.

Data collected through the surveillance system is ultimately shared with the Namibia Medicines Regulatory Council as well as the health ministry.

The information allows the EPI to make decisions on vaccine service delivery and the regulatory authority (and the ministry at large) to take action if safety issues are identified. These include issuing safety communications to patients, healthcare professionals and the community; updating the product information or consumer information about the vaccine; preventing the release of a particular batch of vaccine; restriction of vaccine authorisation to a particular subgroup of the population or withdrawal of vaccine authorisation.

After receiving a vaccine, minor and short-lived symptoms, such as headache, fatigue, fever and chills, muscle and joint pain as well as pain at the side of infection are expected as observed in clinical trials.

Anaphylaxis, a serious, life-threatening allergic reaction may occur very rarely with any vaccine. There were some reports of facial weakness, seizures, loss of sense of taste or smell and cardiac events; however, they have not been confirmed to be causality related to the vaccines.

Two vaccines have been associated with a very rare (1 in every 100 000 vaccine doses) and unusual clotting syndrome with low blood platelet count. This condition is termed Thrombosis with Thrombocytopenia Syndrome (TTS). The overall number of reports received of blood clots in the veins or arteries is no higher than the expected background population rate for the more common type of blood clots in most countries.

There have also been reports of cases of myocarditis and pericarditis reported following vaccination with some mRNA vaccines amongst people aged 30 and younger particularly in male adolescents and young adults. These are very rare and generally mild and respond to conservative treatment such as rest and medication.

It is important to note that for any adverse event that is reported after receiving a vaccine, a causal relationship to the vaccine needs to be established to confirm the true association.

It is worthy of note that the benefits of receiving the Covid-19 vaccines outweigh the risk of experiencing serious side effects or events that have been observed so far.

If you experience any side effects that concern you, please report it to your healthcare worker (doctor, pharmacist, nurse etc.), at the nearest health facility (hospital, clinic, pharmacy etc.) or any vaccination site. You may also call 061 203 2406 for assistance.

* The authors are medicines information and safety pharmacists.